Flexible polymeric packages may be used to hold a variety of products. Such products may be a variety of edible food products such as cheese, meat, crackers, sugar, powdered sugar, flour, salt, and baking soda, or non-food products such as laundry detergent, sand, medical supplies, and other products. Resealable packages are convenient because they can be closed and resealed to preserve and contain the enclosed contents. Resealable packages are also advantageous because they help prevent food products from spoiling and may be opened and closed multiple times.
Zipper closures are often employed to allow a polymeric package to be sealed and re-sealed. These closures are required to both seal the package tightly so that the contents do not leak or spoil, while at the same time allow the closure to be opened and closed without excessive force. To accomplish this, a zipper closure may be designed so that the seal formed by the zipper closure is more secure in the direction facing the contents of the package than the seal is in the direction facing away from the contents of the package. This arrangement allows the package to be opened by the user with a relatively small amount of effort, but also ensures that the package contents are adequately contained against accidental opening.
A problem arises, however, in the manufacture of polymeric packages where the zipper closure must have a certain orientation relative to the rest of the package. Zipper closures are typically provided on a production line as a rolled strip of material. The operator feeds this material into a machine that attaches the zipper closure strip to the rest of the polymeric package. The proper orientation of the zipper closure can be difficult to determine reliably. The features that cause the zipper closure to have a greater sealing force in one direction than the other are not such that they are readily perceptible to the operator. Because of this lack of easy perceptibility, the machine operator may misfeed the zipper closure strip into the manufacturing machinery, causing the resulting package to have sealing forces that are the opposite of that desired. Namely, a misfed zipper closure would result in a package where a greater force is required by the user to open the package and a lesser force seals the contents of the package. It is therefore desired that a zipper closure be configured so that the manufacturing machine operator can reliably and readily feed the zipper closure strip into the machinery in the correct orientation.